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Conference netcad::hub_mgnt

Title:DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:NETCAD::COLELLADT
Created:Wed Nov 13 1991
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4455
Total number of notes:16761

3251.0. "FDDI wrap problem on IMB?" by TKOV51::HAYAKAWA (Kouhei Hayakawa, NPB/MS, Osaka HUB6F) Thu Feb 08 1996 04:09

	Topic 1894 again.
	I tried the following config. If I disconnect the concentrator, 
	FDDI ports on both DECswitch900EFs become listening state by 
	spanning tree protocol. After about 30 second, these ports start 
	forwarding. Is it normal behavier?

MAM   4.1.0
DEFBA 1.5.2
DEF6X 3.1.1
HUBwatch for Windows V4.1.2

Regards,
Kohei
================================================================================
���� 1894.6       Problems hot-swapping DECmultiswitch 900               6 / 7
NPSS::WADE "Network Systems Support"                     30 �� 17-JAN-1995 12:34
--------------------------------------------------------------------------------
    
	I tried the following two configs. Disconnecting the concentrator 
	resulted in an intact FDDI IMB between the two bridges/switches. 

    
                ------------------------------------------------
		|                                               |
External	A						B
	DECswitch 900		Concentrator		DECswitch 900
Internal	B ---------------- A    B --------------- A
T.RTitleUserPersonal
Name		DateLines
3251.1NETCAD::DOODYMichael DoodyThu Feb 08 1996 09:384
    It is expected. It's debatable whether it is desirable. Perhaps 
    Bill will have an update on this.
    
    -Mike
3251.2NPSS::WADENetwork Systems SupportThu Feb 08 1996 11:0936
    Mike, I don't think there's much debate over whether or not it's
    desirable behavior.  This makes the forth customer that  I've heard 
    knocking on the door over this problem.  
    
    Through limited testing in the lab:
    
      IF the EF is configured in a dual ring (external to the DMHUB) and a 
      device is added or removed, the ring wraps and there is no 
      transition to the preforwarding state on the EF FDDI bridge port. 
                                                
      When the EF is attached to the FDDI backplane, adding or removing a 
      module to the FDDI backplane causes the EF to transition its FDDI port to 
      preforwarding.
             
    My understanding of what triggers this transition is the following -
                                   
    	- adding or removing a module to the FDDI backplane LAN causes
    	  the MAM to reallocate the channels

    	- the MAM does this by sending a disconnect to all modules 
    	  residing on the FDDI LAN 

    	- the EF receives the disconnect and sets the state of the FDDI port 
    	  to broken resulting in transitioning the bridge port to preforwarding
                 
    
    All I can say is that its a known problem and its on the list.  
    I suggest that you escalate this as an IPMT into engineering.
    
                      
		Note:  The problem mentioned in note 1894 is unrelated 
    			to this	string.
                                               
    
    Bill